1. Field of the Invention
The invention relates to lamps and, particularly, to a field emission lamp.
2. Description of Related Art
A display device, such as a LCD, often requires a backlight device installed on the backside to provide illumination. Typically, a cold cathode fluorescent lamp (CCFL) has been commonly used as a light source of the backlight device. The CCFL includes a sealed tube and a pair of electrodes respectively disposed at two ends of the sealed tube. A fluorescent layer coated on an inner surface of the sealed tube. The sealed tube is filled with a mixture including an inert gas and mercury vapor. When a voltage is applied to the electrodes, electrons are emitted from the negative electrode. The electrons strike and excite the atom of the mercury vapor and thereby ultraviolet radiation is generated. The ultraviolet radiation in turn strikes the fluorescent layer resulting in visible radiation. However, the mercury vapor, the prominent component of CCFL, is harmful to people and causes environmental pollution.
Field emission lamp without mercury as an alternative light source for backlight devices is also available. This type of field emission lamp includes a cathode and an anode disposed opposite to each other. An electron emitting layer is disposed on the cathode. A fluorescent layer is disposed on the anode. When a predetermined voltage is applied between the cathode and the anode, electrons emitted from the electron emitting layer collide against the fluorescent layer, thereby generating visible light.
However, the electrodes of such mercury free field emission lamp is difficult to manufacture because the cathode and the anode are at the same end of the field emission lamp.
What is needed, therefore, is a field emission lamp with simple structure so as to be much easier on manufacturing.